Stirling Engine Blog Final Report

Stirling Engine Blog Final Report

Due to increased traffic to this blog from people with Whispergen, in particular MicroMon MO related queries, I have decided to upload my project report to give people a sense of what all of this blog is about and was for. I have since finished university (graduated with First Class Honours) and am now hoping to pursue a PhD related to Stirling engine computational modelling. For this reason I do not plan to continue the Stirling engine project related postings.

The full report can be downloaded here:

https://www.dropbox.com/s/9y43gwaecsffgka/Barry_Flannery_BSc_Thesis.pdf

Stirling Engine Blog 22 Feb 18 2013

I have decided to use the Measurement Computing (MCC USB-TC) DAQ for the thermocouple measurements due to its simplicity. I am having some difficulty with this however as the ULx drivers supplied by Measurement Computing are not compatible with LabView 2011. 

I have potentially found a workaround  here: 

http://forums.ni.com/t5/LabVIEW/Does-Universal-Library-Extension-works-for-LabVIEW2011/td-p/1688304

Solving this issue is the last major hurdle in the project. Once I have the data acquisition solved, all that is left is to do is install the remaining hardware. I am undecided whether setting up the pressure transducer is worthwhile as it will involve using the NI USB6211 DAQ and is unlikely to yield any crucial information. Due to project time constraints, I feel that omitting this sensor is the best course of action.

Stirling Engine Blog 21 Feb 14 2013

With the assistance of Umer Khan we figured out how to get the LabView program functioning correctly. There were no errors in the programming, just a subtle sequence to initiating the program. It is necessary to direct the file path to the MicroMon data from the Front Panel VI. Once this is done the program works perfectly.

All that is left to do now is set up the thermocouple data acquisition and have them reading in appropriately. 

Stirling Engine Blog 20 Feb 13 2013

I spent all day today trying to get the LabView program to work but was unable to solve a fundamental issue with reading in live data from a text file.

The crucial half of the program (related to acquiring data from the MicroMon datalog file into LabView) is shown below:

I am working together with Umer to try and solve this issue and have offered him the ability to log in remotely via TeamViewer to review the program as he recalls encountering a similar problem. Solving the LabView program is the last remaining hurdle in the project as everything else has known solutions and can be readily implemented. 

Stirling Engine Blog 19 Feb 12 2013

I decided to draft up a project plan for remaining work in order to get back on track with the project. It is becoming difficult to juggle between the FYP, PhD application and continuing to work towards the degree and I hope that a project plan will allow me best optimise my time.

Additionally, I did some work on Umer Khan's program in order to try and understand it. I am having difficulty getting it to function correctly however. 

Project Plan

Hardware

Software

Flowmeter Buy 2 x ¾” straight compression couplings Plumb flowmeter (mount?) Thermocouples Identify TC sealant method Get TC’s from Thermo lab Install Engine discharge TC Install Engine return TC Install Marine HX Water in TC Install Marine HX  Water out TC Connect all TC to NI DAQ Pressure Transducer Get TK wiring diagram Wire sensor to power supply Thread seal fittings Attach pressure lines Mount in DIN rail box?

LabView Program Bring DAQ home Define program requirements Understand Umer Khan’s program Identify transferable components Program Milestones 1.       NI DAQ reading into LabView 2.       MicroMon data file reading into LabView 3.       Inputs defined and programmed 4.       Outputs defined and programmed 5.       Demonstrate Program stability 6.       Install system in test cell 7.       Capture live data 8.       Run Test

LabView Program Requirements

NI DAQ read in:

• Engine discharge TC
• Engine return TC
• Marine HX Water in TC
• Marine HX  Water out TC
• Pressure Transducer

Read from Measurement File:

• Power
• Fan Speed
• Exhaust Temp
• Pump Frequency

Inputs

• Calorific Value of Diesel (MJ/kg)
• Average Water Flow Rate (lpm)
• File Path (Read from Measurement File)

Outputs

• Heat Output (coolant mass flowrate x ΔT) in kW
• Gross Electrical Output (kW)
• Thermal Efficiency (Heat Output / Heat Input)
• Gross Electrical Efficiency (Electric Out / Heat Input)
• System Efficiency ([Heat output + Gross Electrical Output]/Heat Input)

Test Plan

• Run 4x efficiency tests for repeatability
• Attempt to vary coolant temperatures (up to ~60 celcius)? Run 2x tests

Week 1 (11-15^th Feb)

• Buy 2 x ¾” straight compression
• Bring DAQ home
• Get TC’s from Thermo lab
• Get TK wiring diagram
• Identify TC sealant method 

Week 2 (18-22^nd Feb)

Week 3 (25^th-1^st Feb)

Week 4 (4^th-8^th Mar)

Week 5 (8-15^th March End) 

Stirling Engine Blog 18 Feb 11 2013

I met with Rory and Harald today and filled them in on my trip to the UK and discussed the research direction of the PhD based on that meeting.

Note that I was unable to do any work directly related to the Final Year Project all last week as I was preparing for my trip to Microgen and reading background information on Free Piston Stirling Engines.

Stirling Engine Blog 17 Feb 1 2013

I performed a repeatability test today under the same conditions as the last test. I attained excellent correlation between results which is shown below:

Stirling Engine Blog 16 January 30 2013

I did not do any physical work on the engine today as I was in Thermo King discussing both the project and the PhD application.

Thermo King were kind enough to order me the following (expected within a week):

• Flowmeter for measuring the coolant loop flowrate
• Power supply for the pressure transducer
• Gas Hoses and fittings for connecting to the transducer
• Wall box for mounting the sensors
• Selection of terminal blocks for wiring

Shown below is a similar pressure transducer setup (which I hope to replicate):

Stirling Engine Blog 15 January 29 2013

I ran the engine today for 60 minutes using the new 800 W load. It appears to have worked exactly as planned - the unit's heater clamp did not come on even though the batteries were more or less fully charged at the start of the test. The coolant system reach equilibrium at around 42°C. The system reached steady state around 50 minutes into the test. 

Electric Heater used as battery load

Water condensing out of the exhaust gas (note a single droplet at the base of right angle fitting). The shape of the exhaust flue makes the fowl water drain ineffective and so the water leaks out of the seal. This is not an issue as it can be collected with a drip tray underneath. After about 30 minutes of runtime only about 20ml of water leaked.

Today's key data:

The system reaches a steady state at around 50 minutes into the test. The coolant system stays stabilises at around 42°C with the mains pressure at max flowrate. During efficiency tests, it will be necessary to let the coolant reach its setpoint temperature (60°C) to give a realistic efficiency measurement.

Stirling Engine Blog 14 January 28 2013

As mentioned in previous blog posts, the biggest unresolved problem was connecting the secondary heat exchanger to the mains water tap. It was necessary to join a standard garden hose to 3/4" qualpex - this is a very unusual combination and it is almost certainly not available as a standard fitting in a plumbing shop. I decided to quickly machine a small insert on my lathe that would allow me to join the flexible pipes. Whilst not very aesthetic the jubilee clip/rubber tubing has proven to be extremely effective and simple to use. 

Machining the part from a piece of scrap aluminium

Finished part

Preparing to join the two hoses

The garden hose fits tightly around the insert

The larger diameter hose also fits well. This larger hose just connects onto the qualpex.

Jubilee clips added for additional safety. The interference fit is probably sufficient

I replaced the fitting on the tap with a standard garden hose quick release

With the last of the plumbing problems solved, I hooked up the inverter and a small 250W heater load. I intend on replacing this with an 800W heater in the coming days to act as the proper load for the engine to slow the rate of battery charging.

Batteries and inverter setup

View of the test area (note MicroMon running on the computer)

All of the major systems work on the engine is now completed. There are only minor jobs remaining, mostly related to adding various sensors to the setup which will be logged by LabView.

These include:

• Pressure Transducer - To view the pressure levels inside the engine and keep an eye on any leakage
• Water Flow Meter - T measure the flow rate of mains water pressure through secondary heat exchanger
• Water Flow Meter - To measure the flow rate inside the cooling loop (possibly unnecessary)
• Multiple Thermocouples - To measure heat rejected to cooling circuit and to mains water dump

I also tested the engine with the new secondary heat exchanger dump. It significantly slowed the heating rate of the cooling system. It appeared to stabilise at around 40°C even with around 10 amps going into the heater clamp (the batteries had switched to absorption charge). I ran the engine for a total of about 30 minutes and logged the run using MicroMon.

Today's data. Tblock (blue) is a proxy for the cooling system temperature as both were in rough equilibrium. The key thing to notice is that even with the clamp heater activated, the secondary heat exhanger is able to dump enough heat out of the system to maintain more or less constant coolant temperature. 

Stirling Engine Blog 13 January 26 2013

I did not have time to do any physical work on the engine today. I did however manage to take a look at some of the data taken from Thursday's test run and graph it (shown below).

There are still a number of tasks that remain to be completed before the engine is fully operational:

• Connect Inverter (the battery clips need to be replaced with rings)
• Machine an adapter fitting for the tap (garden hose to 3/4" qualpex)
• Install Labview of the cell computer
• Get a suitably sized load for the inverter (~800 W)

Preliminary view of some key engine parameters (Exhaust Temperature, Engine Block Temperature, Power Output). Note that the data logging was only switched on part way through the engine test and does not have show the engine startup behaviour.

Stirling Engine Blog 12 January 24 2013

I made a good deal of progress today with the engine. I decided to bring in my own drill in order to do some trivial tasks that were taking too long for to be done by others. I mounted the header tank board to the diesel engine frame and I also mounted the coolant pump to the wall. The header tanks are now secure on top of the diesel engine frame and reasonably well isolated from the Stirling engine. 

Exhaust duct in place and header tanks filled and mounted on the secured board

I also spent a good deal of time connecting the new radiator fittings and reinstating the radiator and associated plumbing. As mentioned in the previous blog, I incorporated a drain valve into the system which greatly simplifies draining the whole system.

New valves on the radiator. Note the drain valve on the right hand line of the radiator

After troubleshooting all of the plumbing and bleeding both the coolant and fuel lines of air I proceeded to test fire the engine for a short 10 minute run. It is not possible to run for any longer than this as the heat dump quickly saturates. The engine ran smoothly with no errors. I logged a portion of this data which will be discussed in a later blog.

Stirling Engine Blog 11 January 23 2013

I put the exhaust duct up today, it was relatively straightforward as the flexible duct fits perfectly over the exhaust flue. I am still waiting on the aluminized tape to make a proper seal at the base near the engine.

During the first test charge of the plumbing system (with just water and no glycol), I had a major leak in one of the radiator fittings which forced me to drain the whole system. The radiator had 2 compression fittings connected to it (jury-rigged). The fittings were not the correct fittings for the radiator and were only a temporary measure during the initial tests at home. The thread on the connecting nut appears to be stripped or otherwise damaged. It was necessary to go back to Heat Merchants and pick up some new radiator valves. I've decided to put in the proper radiator valves and use 1/2" to 3/4" straight compression fittings to make them compatible with the qualpex. I've also decided to incorporate a drain valve in the system to make draining the system easier.

Radiator disconnected from circuit

Radiator fitting that needed to be replaced. The thread on the silver hex ring is damaged and it was necessary to replace the whole fitting (this also required getting a radiator spanner - a 1/2" allen key essentially)

Stirling Engine Blog 10 January 22 2013

Pat did an excellent job of making an exhaust pipe. He threaded some thick tubing using a lathe and then welded the joint making it into a single piece. He then gave the tube another pass on the lathe to clean it up so that the whole arrangement fits flush inside of the flexible ducting. I plan to fit the exhaust and duct tomorrow and will use some aluminized tape to seal the joint near the engine exhaust.

Welded gunbarrel fitting with fabricated tubing

Exhaust pipe in place

I connected the fuel line and pump also. I decided to replace the connections on the fuel pump as they were frayed and loose. I used some barrel crimps and positioned them so that polarity reversal wouldn't be possible.

Blue barrel crimps on the fuel pump connections

In addition to the exhaust, I rerouted some of the plumbing to tidy it up but there is still some more work to be done before the rig is in an acceptable condition. Pat also made a stand for the header tanks out of a sheet of plywood. The tanks sit flat on the sheet with their outlets coming out through holes in the sheeting.

Rerouted plumbing (some work still needed). Note white fuel line and coolant header tank (extreme right corner)

All that remains to be done:

• Get the inverter installed and hooked up
• Mount the coolant pump to the wall
• Connect the cold water pipe to the tap
• Charge and bleed the coolant system
• Charge and bleed the fuel system

Stirling Engine Blog 9 January 21, 2013

Pat Donnellan completed the risk assessment today and will prepare the associated paperwork with recommendations. He mentioned that he does not think there will be any major issues that need to be dealt with.

I also completed a "Node Registration Form" for ISS which is required to get the cell computer on the network. Once again, it is not clear what the lead time on this will be. 

There were no technicians on available today to discuss where I could put the header tanks for the engine so physical work on the unit is once again at a standstill. It is hoped that the exhaust fittings will be machined tomorrow and the exhaust can be installed and connected to the cell extraction system.

I purchased a 1000 Watt inverter over the weekend to allow me to connect a standard 240V AC mains load and discharge the battery bank when the engine is generating power. This will prevent the engine from ramping down and dumping current into the clamp heater when the batteries exceed a certain threshold (80% charge).

1000W (24V) Modified Sine Wave Inverter  

Inverter datasheet can be found here (model no. 651.667)

http://www.lrgsoftware.com/files/inverter_datasheet.pdf

Stirling Engine Blog 8 January 18, 2013

A number of significant developments occured today. I was contacted by a former Whispertech employee via the Google blog who was kind enough to share a copy of the MicroMon software with me but more importantly a complete set of instructions accompanied it. I have now discovered what was preventing me from using maintenance mode in the program. A somewhat convoluted set of operations is needed during the install in order to get full functionality from the software.

From the manual:

To access the program, a shortcut to the ".exe" file should be created for the desktop. Firstly, open the folder "C:\Micromon_Release_1_0" and right-click on the file called "MM-Release.exe"; this will bring up a menu where "Create Shortcut" should be selected. Move the newly created shortcut to the desktop by left-clicking the mouse over the shortcut icon and dragging it over to the desktop. Next, right-click on the shortcut and select "Properties" from the menu. In the text box called "Target", the text should read:

C:\Micromon_Release_1_0\MM-Release.exe

In order for the application to work correctly, "-Maintenance-Mode" should be appended to the above. The text should now read:

C:\Micromon_Release_1_0\MM-Release.exe -Maintenance-Mode

[Note that there is a space between the last "e" in "exe" and the hyphen ("-") before Maintenance].

I am now able to utilize the full functionality of MicroMon and have the ability to log and set unit variables. With this significant breakthrough I can now begin building the LabView program to centralize all of the data acquisition.

I made yet another trip to Heat Merchants and DPL to get the remaining plumbing supplies. I've decided to use qualpex and compression fittings for the cooling system connections due to its simplicity. As with the initial testing at home, I am going to use the Thermo King hose and jubilee clips for any remaining joints. I still have to find a way to join the secondary cooling loop to the test cell mains tap. 

Compression fittings installed on the engine

Initial plumbing arrangement. The qualpex will need to be cut to size once the header tank is positioned.

Cooling circuit

Stirling Engine Blog 7 January 17, 2013

Limited progress was made today. I worked on getting network access in the test cell. This involves contacting ISS with the room RJ port number and the test computer's unique identifier (physical address). Both of these pieces of information were forwarded to ISS but there was no indication of lead time on the request. 

RJ port : CR2-050

Physical Address : 00-40-63-E4-EF-20

I met with William Kelly, head of facilities which resulted in some new administrative issues that need to be dealt with before the engine can be commissioned. William highlighted that a risk assessment needed to be done on the project before any further work could be completed. 

William mentioned in particular:

Carbon Monoxide - He mentioned that they have had problems with this in the past.

Diesel handling - He mentioned the risks associated with dermatitis induced by diesel skin contact. 

Mitigating these risks is not going to be an issue. A maximum of 5 litres of diesel will be stored in the engine header tank at any given time and the tank can be filled using gloves with suitable equipment (jerry can with nozzle/hose). Carbon monoxide levels will be negligible at most as the engine utilizes a diesel burner which burns the fuel almost to completion (Nicholas Farra's thesis estimates 99.99%) and any exhaust will be extracted using the exhaust extraction system. As a final layer of protection the cell has multiple toxic gas detectors in case of any build up of CO.

It is worth noting that the test cell was specifically designed for running diesel engines. 

A detailed risk assessment will be undertaken at 12pm on Monday with myself, Rory Monaghan and Pat Donnellan (engineering building safety officer) and any recommendation will be acted on.

Stirling Engine Blog 6 January 16, 2013

The desk finally arrived (courtesy of Pat Kelly). I have set up the various bit of IT hardware and I've organized all of the engine wiring so that it is now neatly coming out the back and allows the unit to be operated with the enclosure in place. I think this is important as I do not want people interfering with the engine inadvertently or otherwise. The engine is now connected to its battery bank and the microprocessor once again has power which will enable me to troubleshoot the MicroMon problems discussed previously.

There are still a number of outstanding issues to be sorted out:

• Engine exhaust - I have bought a 90° gun barrel bend to connect to the exhaust. Pat Kelly says that he can thread a bit of tubing to connect to it. The exhaust ducting can then be placed over this and will be sufficient for removing exhaust fumes.   
• Coolant loop - I need to follow up with the plumbers on the status of the engine's plumbing arrangements. I will most likely go ahead with my own plumbing if this will not be in place by Friday.
• Header tanks - Both the coolant and diesel header tanks will need to be mounted on the wall above the engine. I will need to talk to Pat about the best way to go about doing this.
• Internet Connection - I need to get a longer CAT5 cable to connect to the test cell RJ ports. I may also need to get the ports activated for outside connections.
• Computer Software - I need to install Labview on the server 

Pictures of today's progress are shown below:

View of the test cell before organization

View of the engine wired up

Desk arrangement (note I moved it into the corner as it's neater)

Stirling Engine Blog 5 January 15, 2013

There was no physical work done on the engine  today as I am still waiting on Pat Kelly to deliver the desk to the test cell. Nonetheless I spent a good portion of the day studying some more documentation. I managed to read through two theses from the University of Toronto, both which were based on using the Whispergen PPS16 unit. While the core focus of both papers was not relevant there was still a good deal of useful experimental and hardware related information.  

Efficiency and Emissions study of a Redisdential Micro-Cogeneration System Based on a Stirling Engine and Fuelled by Diesel and Ethanol - Nicolas Farra (Master's Thesis)

https://tspace.library.utoronto.ca/bitstream/1807/25573/1/Farra_Nicolas_201011_MASc_thesis.pdf

Performance Analysis of a Stirling Engine Fuelled by Diesel and Ethanol and Transition to Bio-oil - Charles Habbaky and Adrian Boangiu (BSc Thesis)

http://www.mie.utoronto.ca/undergrad/thesis-catalog/files/130.pdf

I also discovered another interesting piece of market intelligence (conducted by PikeResearch) but sadly it is not publicly available. I intend on doing another trawl on the web using new keywords to see if there are any more recent market/technology intelligence reports related to Stirling cycle combined heat and power technology.

The report:

http://www.pikeresearch.com/research/residential-combined-heat-and-power

Information on PikeResearch (from their website):

Pike Research, a part of Navigant Consulting's global Energy Practice, is a market research and consulting team that provides in-depth analysis of global clean technology markets. The team's research methodology combines supply-side industry analysis, end-user primary research and demand assessment, and deep examination of technology trends to provide a comprehensive view of these industry sectors.

Emerging technology markets are inherently rife with uncertainty and risk. Pike Research provides its clients with market intelligence designed to clarify investment and expansion opportunities for industry participants. Applications for the group's research and analysis include:

• Market sizing and forecasting
• Market segmentation by geography, technology, customer type, end-user market, etc.
• Analyzing the structure of emerging value chains
• Insights on the timing of key market and technology transitions
• Competitive intelligence
• Assessing market demand for new products and assisting with go-to-market strategies
• Providing inputs for business planning, budgeting, and forecasting
• Benchmarking companies within the competitive environment

An interesting site that I came across that I need to investigate more thoroughly:

http://www.cospp.com/cogeneration-chp/micro-chp.html

In addition to reading the theses I decided to email many of the major Stirling engine manufacturers requesting information and advice in relation finding out the current state of the industry. Due to the difficulty in accessing up to date market intelligence (they are all secured behind immense paywalls) this was the only remaining course of action. I do not expect much from this but it was worth a try.

Companies contacted:

• Sunpower
• Microgen
• Infinia
• Stirling BioPower
• Efficient Home Energy (Whispertech successor)

Stirling Engine Blog 4 January 14, 2013

I met with Pat Kelly and two of the Engineering department plumbers today to discuss what work would be needed to get the engine commissioned. They are going to make up the required plumbing and they also agreed that it is a relatively simple job to get it commissioned. Pat is also working on getting a desk for me and dealing with the exhaust ducting. I hope that this will be done soon as it will allow me to begin working on some of the other aspects of the system for example the data acquisition. 

The rest of the day was spent reading the remainder of the EPRI literature and communicating with Umer Khan in relation to the MicroMon installation bugs. It will not be possible to troubleshoot this problem until I have the engine IT hardware set up in the test cell - dependent on getting a desk. Umer also kindly offered to use remote access software to view the problem himself, again this is dependent on getting the apparatus set up. I intend on keeping in regular contact with the technical staff in Engineering to ensure good progress is being made.

I also came across a very recent document (June 2012) reviewing the current state of the art in Stirling engines for CHP which lists the current players that have or are soon to release commercial engines. The document can be found here below and some of the key tables have been included below for brevity. 

A Review of Stirling Engine Technologies applied to micro-Cogeneration Systems

http://www.ecos2012.unipg.it/public/proceedings/pdf/SECS/SECS_ecos2012_338.pdf

I also came across some other interesting papers and documents on the state of Stirling engine technology:

Technological development in the Stirling cycle engines (2008)

• http://penge.novatron.hu/zene/STIRLING%20E-Books/Technological%20development%20in%20the%20Stirling.pdf

A review of solar-powered Stirling engines and low temperature differential Stirling engines (2003)

• http://www.inference.phy.cam.ac.uk/sustainable/refs/solar/Stirling.pdf

DFE2008 Residential Micro-cogeneration (Wiki)

• http://en.wikiversity.org/wiki/DFE2008_Residential_Micro-cogeneration 

Residential Cogeneration Systems: A Review of The Current Technologies (2005)

•  http://www.ecbcs.org/docs/annex_42_Review_Residential_Cogen_Technologies.pdf